PHP Tutorial - Lesson 3: Introduction to PHP - Part II

Arrays

What is a variable?

• A variable is a storage area that holds only one value.

What is an array?

• A special variable that holds multiple values.

• One of the most powerful properties in php is Arrays.

• PHP arrays have a property of being dynamic, that it is not limited with a size for it, you can add elements to it as needed.

• Arrays in php also loosely typed.

• There are three kinds of arrays in php, numeric, associative, and multidimensional. Each kind has its area of usability.

Numeric array: zero-based index.

• You can declare numeric array in php in more than one method.

Example:

<?php

$age= array(“30”,”21”,”19”);

$age[3] = “17”;

$age[]= “35”;

echo $age[0].” “.$age[1].” “.$age[2].” “.$age[3].” “.$age[4];

?>

• Previous script shows you how powerful it is to an array to be dynamic, so you can expand it as needed.

• You can declare array and initialize it with values like $age = array(“value1”,”value2”)

• You can expand it, by two methods. if you know the last index value, then next index will be last index+1. $age[3]=“17”;

• If you don’t know what was last index you can use this great way $age[] = “value”;

• This will add the new value to the bottom of the array.

Access Array values:

• It is inconvenient to access each element of the array by entering its index, suppose you are talking about an array of 1000 elements, shall you access it line by line? It is not a programmer idea.

• Now we’ll talk about special kind of loops which is foreach loop.

Foreach loop:

• Syntax: foreach($array as $value)

• {

• Your code…

• }

• This kind of loop usually is used when dealing with arrays. Because you don’t know what is the size of the array, and you might need to access each element of the array.

Example:

<?php

$arr[]=“one”;

$arr[]=“two”;

$arr[]=“3”;

foreach($arr as $value) echo $value.” “;

?>

Notes:

• We declared an array called arr. Then we added values to it.

• Latest thing, we accessed each element of the array using the foreach loop, which will loop through each element of the array.

Associative array: an array in which each id is associated with a value.

• When storing data about specific named values, a numerical array is not always the best choice to do it.

• In associative arrays, we can use values as keys and assign values to it.

Example:

<?php

$age = array(“anas”=>20, “ahmad”=>21, “abd”=>22);

$age[‘mohammad’]=19;

echo “anas is “.$age[‘anas’].” years old”;

?>

Multidimensional array: each element in the array could be an array. And each element in the sub array could also be an array.

Example:

<?php

$student = array(“anas”=>array(“0700901055”,”computer science”) , “ahmad”=>array(“0700902034”,”computer information system”, “Third year”) );

echo “anas information”.$student[‘anas’][‘0’].” “.$student[‘anas’][‘1’];

?>

To download this lesson as PDF file click here: PHP Tutorial - Lesson 3: Introduction to PHP - Part II

Best Wishes,

Anas Jaghoub